The present invention relates to the stretching of plastic sheets and, more particularly, to the stretching of plastic sheets of non-circular configuration, particularly of acrylic resin composition.
Because of its strength, formability, and light transmission characteristics, various plastic materials, such as acrylic resins, and more particularly, polymerized acrylates, preferably polymerized polymethyl methylacrylate, have a variety of uses and particularly have been used to form windows and canopies for aircraft. Manufacture of the plastic window often involves a stretching step in which an as-cast blank of plastic or acrylic material is heated and stretched to enhance its physical characteristics and/or to provide the treated acrylic sheet that results with a required curvature.